#!/bin/python

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    #min 6
    #1 digit
    #1 lower
    #1 upper
    #1 special
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    
    has_numbers = False
    has_lower_case = False
    has_upper_case = False
    has_special_characters = False
    #figure out numbers, UC, LC, special, that are missing
    #if < 6 add anything
    for i in numbers:        
        if password.find(i) > -1:
            has_numbers = True
    for i in lower_case:
        if password.find(i) > -1:
            has_lower_case = True
    for i in upper_case:
        if password.find(i) > -1:
            has_upper_case = True            
    for i in special_characters:
#        print i + str(password.find(i))
        if password.find(i) > -1:
            has_special_characters = True
            

    stronger = int(not has_numbers) + int(not has_lower_case) + int(not has_upper_case) + int(not has_special_characters)

#    print has_numbers
#    print has_lower_case
#    print has_upper_case 
#    print has_special_characters
    return max(stronger,6-n)
    
            

if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    answer = minimumNumber(n, password)
    print answer